In various types of valves, i.e. double seat valves also known as mixproof valves, it is commonly known to clean a valve seat by circulating cleaning liquid through said open valve seat. The cleaning is carried out for hygienic reasons and is normally carried out in an automatic manner with a certain time interval or the like.
The valve can be cleaned with the valve seat fully open but the cleaning is mainly carried out with a partly open valve seat to minimize the amount of used cleaning liquid and at the same time a partly open valve seat also has the advantage that a flow of cleaning liquid is flushed through at the exact place that is to be cleaned. The valve seat to be cleaned can be positioned in-stream or end-stream.
In the known solutions such a cleaning has to be carried out as described above or by a manual cleaning, where the valve parts are cleaned as effectively as possible, leaving some areas in the valve in a somewhat unclean state.
An example of a known solution can be seen in U.S. Pat. No. 4,552,167, which describes a cleaning system for cleaning one or more valve seats with a cleaning agent.